The more subtle side of this can be made clear though, in realising that this altering of what is and what is not advantageous from era to era is entirely unpredictable to us. We perceive certain things as ‘good’ attributes (commonly: Sharp teeth, strong muscles, fast runner, intelligence) and other things as ‘bad’ attributes (commonly: obesity, skin prone to sunburn, unco-ordination) and we decide that anything which departs from the good and/or acquires more bad attributes is losing its selective advantage. While this may often be true, the fact of the matter is that our own judgement has been crafted by evolution and we are biased in our judgements towards the things which were adaptive in the past. We have no idea what is going to happen next and so we can’t be sure that our crafted judgements are any longer valid. As well as that we have no way of knowing what hidden benefits may lay under some superficial phenotype. Combine these two consideration and you are faced with a situation in which you may have superficially ‘bad’ (according to our current judgement) phenotypes with underlying attributes which may in the next few hundred generations come to be so advantageous that they create a selective pressure in themselves. Darwin himself observed that “the struggle will generally be more severe between species of the same genus, when they come into competition with each other, than between species of distinct genera,” [6] and so it is with humans already, and probably will continue to become more and more as we reach the limits of our extended niche. What variation it is that holds the key to the adaptive advantage is surely unknown to us, but it seems incredibly unlikely that the advantage will be with those able to outrun or successfully hunt a lion.
On a less subtle level though there is one more element within this class of error that is ignored by people who claim that humans are no longer evolving. Natural Selection is thorough. Amongst all of the variation which we can and cannot discriminate superficially, Natural Selection screens everything. Natural Selection, unlike our ability to pass judgement, is an unrelenting eternal force sifting through every single probabilistic relation within an organism, between members of a community, between organisms in a species, and between an organism and its environment; all at once. To say that modern humans are no longer under a selective pressure is to claim two things: It is claiming that we know what Natural Selection works on; and it claims that we have used this knowledge to control every single instance of potential selective pressure. We certainly do not know this, and we most certainly have not controlled it. Humans are just as subject to selective pressures as every other organism, even if we can’t see them.
Class 2
The second category of error is simply a case of forgetting that there is more to selective pressures than mere survival. The need to procreate is just as important in evolution, and to procreate humans need to find mates. Sexual selection is present throughout nature and is undoubtedly present in Homo sapiens too. One theory even claims that our enlarged brains, our paedomorphic ape appearance, the size difference between males and females, and various other factors are all consequences of sexual selection [7]. Medicines, technology and abundant shelter will never affect the role sexual selection plays in the evolution process, but culture itself may. It is almost impossible to guarantee that our sexual desires, choices and behaviours are guided by our own and our potential mate’s genetic make up, rather than being guided by the culture we live in. To make it a little more complicated, its not even easy to figure out whether our culture is largely guided by our genetic make up, and therefore only an intermediate between our genes telling us what we want and what we actually choose. Whatever the case one fact remains: Sexual selection - on whatever level – occurs. As long as it continues to occur there will be a selective pressure present, and evolution will occur.
Class 3
The third category of error is the belief that the entire world is like the society we are lucky enough to live in. A society where medicine is provided for everyone, where housing is plentiful, where there is available electricity, running water etc. The fact of the matter is that this isn’t the case at all, but instead around 80% of the world’s population lives in developing countries [6]. If we are to talk about the evolution of Humans and we want to focus on one lifestyle, it would in fact make much more sense to focus on developing countries and talk about their way of life. Of course though, if we were to do this, then most of the points raised about medicines, technology, distribution of food, and general ease/comfort of life would no longer apply, and there would be no case. Obviously when the claim ‘Humans are no longer evolving’ is made, the claim is actually meant to be ‘Humans in developed countries are no longer evolving.’
Class 4
The fourth class of error actually intermingles with every other class on some level. Evolution takes many thousands of years to occur and must be discussed accordingly. To talk only about the way things are now and then to try to infer facts about evolution from that flash of existence, is to fall into this error.
This particular error is all encompassing in its nature and is the sort of error that humans are very prone to make. Being organisms that deal with time in units like seconds, minutes, hours, years, and even up to decades, the concept of hundreds of years or several hundred years turns into ‘A long time’ and nothing else. To think of a hundred years, is to think of something only just graspable. To think of a thousand years though, is really something beyond our grasp and we tend to resort to ‘a really long time’ and that is as far as our imagination goes. We may be able to grasp some sort of awe over the length of it, but we do not comprehend it. Tens of thousands of years, millions of years, billions of years all meld into this one conception of ‘a really long time’ and nothing else. There is little meaning in any of it. To then speak of evolution, something which takes thousands of years for any real changes to start being apparent, is to talk of something which we can’t grasp the timeframe of. Falling into this class of error when talking about Evolution is almost inevitable for anyone not consciously aware of this problem.
Understanding now that evolution only works over the course of many thousands of years means that the claim that ‘humans are no longer evolving’ translates into ‘humans will not evolve at all over the next few thousand years’. Realising this, to maintain the claim that humans are no longer evolving is to claim that our control over our environment is so all encompassing and so certain that nothing that happens will break our control. It is a claim that we will never run out of food, that our population growth will never reach maximum capacity, that rising waters will never cause massive loss of farmland or living space, and that no virus or bacterial pathogens will ever break out into a pandemic. It is to claim that humankind has already completely conquered nature in all of its forms.
Whether we accept evolution as something that occurs with or without a selective pressure, the arguments presented to show that humans are no longer evolving tend to become meaningless in light of how evolution actually works. The points may seem valid in some regard, but they all miss a vital point somewhere and so can be easily shown as the empty claim they are. Humans are varied, humans are being selected, and a time will come not so far off in the future when massive selection may be applied as a consequence of our own actions. Humans are still evolving.
References
1. Webster’s 1828 dictionary, http://www.christiantech.com/
2. Chris Colby. Introduction to Evolutionary Biology, Version 2. 1996.
http://talkorigins.org/faqs/faq-intro-to-biology.html
3. A. Eyre-Walker, P.D. Keightley. 1999. High genomic deleterious mutation rates in hominids. Nature 397:344-347
4. B Alberts, A Johnson, J Lewis, M Raff, K Roberts, P Walter. 2002. Molecular Biology of the Cell 4th Edition, Chapter 4, p 202, table 4-1.
5. D Dennett. 1995. Darwin’s Dangerous Idea: evolution and the meaning of life. New York. p 343
6. C Darwin. 1859. The Origin of Species, first edition, reprinted in penguin classics 1985, chapter 3:p127.
7. D Brin. 1996. Neoteny and Two-Way Sexual Selection in Human Evolution. Journal of Social and Evolutionary Systems 18(3):257-276
8. http://www.unfpa.org/sustainable/demographics.htm
